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R Séguin

Publications and source records attributed to R Séguin.

10 recordsLinked to original sources
PubMed1999

Sensitized lymphocytes and CD40 ligation augment interleukin-12 production by human dendritic cells in response to Toxoplasma gondii.

Dendritic cells (DC) are potent antigen-presenting cells that can stimulate T cell responses by secreting cytokines. During Toxoplasma gondii infection, host immunity is mediated by interferon-gamma, which is induced by interleukin-12 (IL-12). Whether T. gondii infection would stimulate human DC to produce IL-12 was determined. DC were generated from human peripheral blood mononuclear cells cultured with recombinant human granulocyte-macrophage colony-stimulating factor and recombinant human IL-4. DC secreted high levels of IL-12 in response to lipopolysaccharide but not to either live T. gondii tachyzoites or soluble antigen. However, IL-12 production in response to T. gondii was observed when DC were cocultured in contact with lymphocytes isolated from seropositive donors. Ligation of CD40:CD154 was partially essential for IL-12 secretion. These data demonstrate that signals obtained from contact with sensitized lymphocytes are critical for human DC to secrete IL-12 in response to T. gondii.

Animals↗
PubMed1997

The tumor necrosis factor alpha-stimulating region of galactose-inhibitable lectin of Entamoeba histolytica activates gamma interferon-primed macrophages for amebicidal activity mediated by nitric oxide.

Entamoeba histolytica adheres via galactose-lectin (Gal-lectin) to human colonic mucins and intestinal epithelial cells as a prerequisite to amebic invasion. Native Gal-lectin is a protective antigen in the gerbil model of amebiasis. Amino acids 596 to 1082 of Gal-lectin mediate E. histolytica adherence to target cells and stimulate tumor necrosis factor alpha (TNF-alpha) production by naive murine bone marrow macrophages (BMM). Resistance to amebiasis requires an effective cell-mediated immune response against E. histolytica trophozoites mediated by nitric oxide (NO) released from activated macrophages. Herein, we determine whether the TNF-alpha-stimulating region of Gal-lectin can activate gamma interferon (IFN-gamma)-primed BMM for NO production and amebicidal activity. Native Gal-lectin (100 to 500 ng/ml) stimulated TNF-alpha and inducible nitric oxide synthase (iNOS) mRNA expression in IFN-gamma-primed BMM as did lipopolysaccharide (100 ng/ml). Primed BMM produced TNF-alpha and NO in response to Gal-lectin in a dose-dependent manner. Antilectin monoclonal antibody IG7, which recognizes a domain (amino acids 596 to 818) of the TNF-alpha mRNA-stimulating region of Gal-lectin, specifically inhibited TNF-alpha and iNOS mRNA induction and TNF-alpha and NO production by primed BMM in response to Gal-lectin (100 ng/ml). Simultaneous treatment of BMM with IFN-gamma and Gal-lectin (100 ng/ml) activated the cells to kill E. histolytica trophozoites, whereas IFN-gamma treatment alone had no effect. In the presence of monoclonal antibody 1G7 or aminoguanidine (an iNOS inhibitor), NO production and amebicidal activity were inhibited >80%. These results suggest that the TNF-alpha-stimulating region of native Gal-lectin is a potent stimulus of IFN-gamma-primed BMM for NO production, which is essential for host defense against amebiasis.

Animals↗
PubMed1995

Identification of the galactose-adherence lectin epitopes of Entamoeba histolytica that stimulate tumor necrosis factor-alpha production by macrophages.

The 170-kDa subunit of the galactose-adherence lectin (Gal-lectin) of Entamoeba histolytica mediates adherence to human colonic mucins and intestinal epithelium as a prerequisite to amebic invasion. The Gal-lectin is an immunodominant molecule and a protective antigen in the gerbil model of amebiasis. Tumor necrosis factor alpha (TNF-alpha) produced by activated macrophages enhances nitric oxide-dependent cytotoxicity in host defense against E. histolytica. The purpose of this study was to identify the Gal-lectin epitopes which stimulate TNF-alpha production by macrophages. Murine bone marrow-derived macrophages (BMMs) exposed to Gal-lectin (100-500 ng/ml) stimulated stable expression of TNF-alpha mRNA (8-fold increase) and TNF-alpha production similar to that of lipopolysaccharide-stimulated cells (100 ng/ml). Polyclonal anti-lectin serum specifically inhibited TNF-alpha mRNA induction in response to the Gal-lectin but not to lipopolysaccharide. Anti-lectin monoclonal antibodies 8C12, H85 and 1G7, which recognize nonoverlapping epitopes of the cysteine-rich region of the 170-kDa heavy subunit, inhibited both amebic adherence to mammalian cells and Gal-lectin-stimulated TNF-alpha mRNA expression by BMMs,but monoclonal antibody 7F4 did neither. As these inhibitory antibodies map to amino acids 596-1082 of the 170-kDa Gal-lectin, our results have identified the functional region that mediates amebic adherence and TNF-alpha mRNA induction in BMMMs; thus, this region of the Gal-lectin is a subunit vaccine candidate.

Animals↗
PubMed1992

Five-month-old girls' and boys' exploratory behaviors in the presence of familiar and unfamiliar toys.

The exploratory behaviors of 60 5-month-old girls and boys were observed as they played with three unfamiliar toys and one familiar toy of their own during a laboratory session. Infants were seated at a table on the lap of an assistant. Each toy was placed on the table and remained there for 2 min after the infant first touched it. Frequency and duration of visual fixation on the toy, hand contact with the toy, five categories of lateralization, and eight categories of handling behaviors were measured. On the whole, the exploratory behaviors of girls and boys were not markedly different. However, girls spent more time than boys did in simultaneous hand contact with and visual fixation on their own familiar toy, whereas boys made more frequent contact with the familiar toy without visual fixation. In addition, boys displayed, overall, more tapping behaviors, and girls, more pinching and object-displacement behaviors. Girls and boys did not differ in manual lateralization. Results are discussed in reference to infants' rate of development, motor activity level, and girls' and boys' reactions to novelty.

Attention↗
PubMed1983

Bowel displacement due to psoas muscle hypertrophy.

Extrinsic compression of the medial border of the ascending colon and bilateral small bowel displacement at the lumbosacral level were observed in a sportswoman. Psoas muscle hypertrophy was confirmed by computed tomography. This entity should be added to the differential diagnosis of bowel displacement.

Adult↗
PubMed1982

Narrowband teleradiology.

A narrowband communication system using the Canadian satellite ANIK-B was used to transmit radiographic images from northern Quebec to Montreal. This slow scan television (SSTV) system was used to study the accuracy of the radiologist's interpretation, both with samples of pre-selected films and current patients. Several hours of training in the technique of radiographic interpretation from a static image displayed on a TV monitor was an important factor affecting performance. In selected patients, based on a sample of 124 error-free direct viewing interpretations by four radiologists, SSTV reading by the same fully trained radiologists was correct in 84.5%. With actual patients, and assuming the interpretation from direct viewing to be the correct one, SSTV reading of the radiographs by the same radiologist gave a corresponding figure of 84.1% in a sample of 518 patients containing 73.4% of negative findings, and 89.4% in another sample of 305 patients, including 82% of negative findings. The present error rate on SSTV reading is twice as great as radiographic interpretation using a broadband television system.

Canada↗
PubMed1981

Teleradiology in northern Quebec.

A two-way television network using the Canadian satellite ANIK-B was utilized to transmit radiographic images from Northern Quebec to Montreal. The accuracy of the radiologist's interpretation and his satisfaction with the TV system were studied using a series of 67 preselected cases and 425 current clinical cases. The four participating radiologists gave correct TV interpretations in 81% of the 39 selected cases presented at the beginning of the experiment. This value reached 94% for the other 28 selected cases presented after three months of regular use of the TV system. With current clinical cases, the agreement between TV and direct interpretations was 93%. Although magnification was available, correct identification of very small lesions proved to be the major source of error. On the whole, the radiologists were satisfied with the TV system.

Adult↗